Irradiance data in Tokyo is downloaded from Japn Meteorological Agency. The data is from 2012.1.1 to 2018.1.1.

head(data)

##         Date Irradiance
## 1 2012-01-01       8.02
## 2 2012-01-02       8.14
## 3 2012-01-03       8.59
## 4 2012-01-04      10.49
## 5 2012-01-05      11.29
## 6 2012-01-06       9.89